You are using Bushbox ASH, in case you need to search for details.
Same as any other shell program, just "source", A.K.A ".", a script file having the commands you need to get yourself setup as desired.
Sure, you do have to type the name of that "source filename" shell script.
But that shouldn't be too much work.
(If it is, stop thinking of using the command line for anything, you will be doing a lot of typing.)